From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754223Ab1KGPdE (ORCPT ); Mon, 7 Nov 2011 10:33:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:25435 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979Ab1KGPdB (ORCPT ); Mon, 7 Nov 2011 10:33:01 -0500 Date: Mon, 7 Nov 2011 16:32:20 +0100 From: Andrea Arcangeli To: Nai Xia Cc: Hugh Dickins , Mel Gorman , Pawel Sikora , Andrew Morton , linux-mm@kvack.org, jpiszcz@lucidpixels.com, arekm@pld-linux.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mremap: skip page table lookup for non-faulted anonymous VMAs Message-ID: <20111107153220.GD3249@redhat.com> References: <201111071221.35403.nai.xia@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201111071221.35403.nai.xia@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 07, 2011 at 12:21:35PM +0800, Nai Xia wrote: > If an anonymous vma has not yet been faulted, move_page_tables() in move_vma() > is not necessary for it. I actually thought of adding that (in fact fork has it and it's more likely to be beneficial for fork than for mremap I suspect), but this adds a branch to the fast path for a case that shouldn't normally materialize. So I don't think it's worth adding it as I expect it to add overhead in average. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id E70DE6B0080 for ; Mon, 7 Nov 2011 10:32:30 -0500 (EST) Date: Mon, 7 Nov 2011 16:32:20 +0100 From: Andrea Arcangeli Subject: Re: [PATCH] mremap: skip page table lookup for non-faulted anonymous VMAs Message-ID: <20111107153220.GD3249@redhat.com> References: <201111071221.35403.nai.xia@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201111071221.35403.nai.xia@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Nai Xia Cc: Hugh Dickins , Mel Gorman , Pawel Sikora , Andrew Morton , linux-mm@kvack.org, jpiszcz@lucidpixels.com, arekm@pld-linux.org, linux-kernel@vger.kernel.org On Mon, Nov 07, 2011 at 12:21:35PM +0800, Nai Xia wrote: > If an anonymous vma has not yet been faulted, move_page_tables() in move_vma() > is not necessary for it. I actually thought of adding that (in fact fork has it and it's more likely to be beneficial for fork than for mremap I suspect), but this adds a branch to the fast path for a case that shouldn't normally materialize. So I don't think it's worth adding it as I expect it to add overhead in average. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org